1. Field of the Invention
The present invention relates to an inflatable cuff which is cylindrically wound around a body portion of a living subject so as to press the body portion in measuring a blood pressure of the subject.
2. Discussion of Related Art
There is known an inflatable cuff which is cylindrically wound around a body portion of a living subject so as to press the body portion in measuring a blood pressure of the subject. The inflatable cuff includes a belt-like elongate bag which is formed of a nylon resin cloth, and a rubber-made inflatable bag accommodated in the belt-like elongate bag. Alternatively, the inflatable cuff includes a belt-like elongate bag which is formed by folding a vinyl resin sheet, and a portion of the elongate bag is high-frequency welded so as to define an air-tight inner space functioning as an inflatable bag.
In measuring a blood pressure of a patient, the inflatable cuff which is connected to a blood pressure (BP) measuring apparatus is wound around a body portion of the patient. The BP measuring apparatus increases the pressure of the inflatable cuff up to a target pressure value which is pre-determined to be higher than a systolic blood pressure of the patient, subsequently slowly decreases the cuff pressure, and measures blood pressure values of the patient during the slow decreasing of the cuff pressure. Described in detail, the pressure oscillation produced in the inflatable bag of the cuff is detected as a pulse wave, and the systolic and diastolic blood pressure values of the patient are determined based on the change of respective amplitudes of successive heartbeat-synchronous pulses of the pulse wave. During the blood pressure measurement with the inflatable cuff being wound around the body portion of the patient, the patient undesirably suffers from subcutaneous bleeding in the skin of the body portion which is pressed by the inflatable cuff, due to strong friction locally caused between the inner surface of the inflatable cuff and the skin of the patient which is held in direct contact with the inner surface of the cuff. In particular, old-aged patients whose blood capillaries are weak tend to suffer from the problem.
It is therefore an object of the present invention to provide an inflatable cuff used for measuring a blood pressure of a living subject, which cuff prevents the skin of a body portion of the subject around which the cuff is wound, from suffering from subcutaneous bleeding.
As a result of an extensive study made by the inventors of the present invention, it has been found that the skin of the subject is locally pinched and corrugated by the inner sheet member of the cuff when the skin of the subject is pressed by the inflatable bag which has been inflated, due to large friction caused between the inner sheet member of the cuff which is positioned between the inflatable bag and the skin of the subject, and the skin of the subject which is held in direct contact with the inner sheet member. In this case, the skin of the subject is likely to suffer from the subcutaneous bleeding. The inventors have also found that the skin of the subject can be protected from suffering from the subcutaneous bleeding if the inflatable bag and the inner sheet member are easily slidable relative to each other.
The above object may be achieved according to a principle of the present invention, which provides an inflatable cuff for being wound and inflated around a body portion of a living subject to press the body portion in measuring a blood pressure of the subject, the cuff comprising: an inflatable bag; and an inner sheet member and an outer sheet member which are positioned inside and outside the inflatable bag, respectively, when the cuff is wound around the body portion of the subject; wherein at least a portion of the inner sheet member that is positioned inside the inflatable bag includes at least two layers which are separate from, and superposed on, each other.
In the present cuff wherein at least a portion of the inner sheet member that is positioned inside the inflatable bag is formed by at least two layers which are separate from, and superposed on, each other, one of the two layers which is adapted to be held in contact with the skin of the subject, and the other layer which is located on the side of the inflatable bag are permitted to be movable relative to each other in directions parallel to the two layers. Further, the above-indicated other layer which is located on the side of the inflatable bag can be formed by using a material which is easily slidable relative to the inflatable bag. Accordingly, the present arrangement is effective to prevent the skin of the subject from suffering from the subcutaneous bleeding which arises from strong friction between the cuff and the skin of the subject which is pressed by the cuff.
Preferably, the two layers of the inner sheet member are bonded to each other at respective peripheral portions thereof, so that a remaining portion of at least one of the two layers is movable relative to a remaining portion of the other layer in directions parallel to the two layers.
Preferably, the two layers comprise a bag-side layer which is located on the side of the inflatable bag, and a contact layer which is adapted to be held in close contact with the body portion of the living subject when the cuff is wound around the body portion, the bag-side layer being formed of a stretchable material. Preferably, the bag-side layer is formed of a material selected from the group consisting of a natural fiber woven fabric, a natural fiber unwoven fabric, a synthetic fiber woven fabric, and a synthetic fiber unwoven fabric, the contact layer being formed of a material selected from the group consisting of a long-fiber woven fabric and a long-fiber unwoven fabric. At least one of the natural fiber woven fabric and the natural fiber unwoven fabric preferably comprises at least one of a cotton fabric, a silk fabric, and a wool fabric. This arrangement permits easy sliding and easy displacement of the contact layer which is held in close contact with the skin of the subject and the bag-side layer which is located on the side of the inflatable bag, relative to each other, in directions parallel to the two layers.